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Switch to use cutlass.utils.get_smem_capacity_in_bytes #1906

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Merged
tridao merged 1 commit into from
Sep 24, 2025
Merged

Switch to use cutlass.utils.get_smem_capacity_in_bytes #1906

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4 changes: 2 additions & 2 deletions flash_attn/cute/flash_bwd.py
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@
import cutlass
import cutlass.cute as cute
from cutlass.cute.nvgpu import cpasync, warp
import cutlass.utils.ampere_helpers as sm80_utils_basic
import cutlass.utils as utils_basic

from flash_attn.cute import ampere_helpers as sm80_utils
from flash_attn.cute import utils
Expand Down Expand Up @@ -125,7 +125,7 @@ def can_implement(
smem_usage_V = n_block_size * head_dim_v * 2
smem_usage_QV = (smem_usage_Q + smem_usage_V) if not V_in_regs else max(smem_usage_Q, smem_usage_V)
smem_usage = smem_usage_QV + smem_usage_dO + smem_usage_K
smem_capacity = sm80_utils_basic.SMEM_CAPACITY["sm80"]
smem_capacity = utils_basic.get_smem_capacity_in_bytes("sm_80")
if smem_usage > smem_capacity:
return False
return True
Expand Down
4 changes: 2 additions & 2 deletions flash_attn/cute/flash_fwd.py
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@
import cutlass.cute as cute
from cutlass import Float32, Int32, const_expr
from cutlass.cute.nvgpu import cpasync, warp, warpgroup
import cutlass.utils.ampere_helpers as sm80_utils_basic
import cutlass.utils as utils_basic
import cutlass.utils.hopper_helpers as sm90_utils_basic

from flash_attn.cute import ampere_helpers as sm80_utils
Expand Down Expand Up @@ -127,7 +127,7 @@ def can_implement(
smem_usage_QV = (smem_usage_Q + smem_usage_V) if not Q_in_regs else max(smem_usage_Q, smem_usage_V)
smem_usage = smem_usage_QV + smem_usage_K
# TODO: sm86 and sm89
smem_capacity = sm80_utils_basic.SMEM_CAPACITY["sm80"]
smem_capacity = utils_basic.get_smem_capacity_in_bytes("sm_80")
if smem_usage > smem_capacity:
return False
# Check if twice the block size is divisible by the number of threads
Expand Down